FlpER

FlpER is a recombinase enzyme derived from the Flp recombinase system of the yeast Saccharomyces cerevisiae. The "ER" in FlpER typically refers to estrogen receptor, indicating that Flp recombinase activity is controlled by the administration of estrogen or a synthetic estrogen analog like tamoxifen. This inducible system allows for precise temporal and spatial control over DNA recombination events.

The FlpER system functions through site-specific recombination. Flp recombinase recognizes and binds to specific DNA sequences called Flp recognition target (FRT) sites. When two FRT sites are present on the same DNA molecule, Flp recombinase can catalyze a recombination event, leading to the excision, inversion, or insertion of the DNA segment between the FRT sites, depending on their orientation.

The inducible nature of FlpER is achieved by fusing the recombinase protein to a mutated ligand-binding domain of the estrogen receptor. In the absence of estrogen, the fusion protein is sequestered in the cytoplasm. Upon administration of estrogen or tamoxifen, the ligand binds to the receptor domain, causing a conformational change that allows the fusion protein to translocate into the nucleus. Once in the nucleus, FlpER can access and act upon the FRT sites, initiating recombination. This controllability makes FlpER a valuable tool in genetic engineering, particularly in research settings involving developmental biology and neuroscience, where precise control over gene expression or gene modification is crucial.